Theorie

Due to recent technological developments, tapered optical fibers (TOFs) can be produced with waist diameters smaller than the wavelength of the guided light. In the waist region of such TOFs, the core of the original optical fiber is almost vanishing and the light-guiding properties are determined by the refractive index of the original cladding and the refractive index of the surrounding vacuum/air. Such subwavelength-diameter vacuum-clad dielectric-core fibers are called nanofibers. Due to adiabatic tapering, the transmission of TOFs with a nanofiber waist can be as high as 99%. In conjunction with the strong lateral confinement and the pronounced evanescent field of the nanofiber-guided light, this makes them versatile devices for efficiently coupling light and matter.

Over the past years, various aspects of nanofiber-based quantum optics and nanophotonics have been investigated. It has been shown that nanofibers can be used to trap, manipulate, and guide atoms, to provide efficient coupling of light to micro- and nanostructures, and to probe atoms, molecules, and nanoparticles at or near the nanofiber surface.

The overall goal of the present theoretical research is to investigate new approaches to fundamental and applied problems of classical and quantum electrodynamics offered by the novel TOF experimental setup. Our theoretical research focusses on the following specific topics:

(1) The mechanical effects of a negative Poynting vector of the evanescent field of a nanofiber on nanoparticles.

The main goals of subproject (1) are to clarify the relation between a negative Poynting vector and the orientation of the optical force acting on a nanoparticle in the vicinity of a nanofiber as well as to search for appropriate conditions under which nanoparticles are dragged towards the light source.

In subproject (2), the goals are to study the interaction between a nanofiber-cavity mode and a linear array of atoms and to examine the effect of electromagnetically induced transparency in such a nanofiber-based system with the aim of using the system for highly efficient storage and retrieval of quantum information as well as for implementing practical schemes for quantum gates and quantum switches based on this nanofiber-CQED system.

The recent results of our research have been reported in the following publications: